1. Field of the Invention
The present invention relates to a multi-core optical fiber.
2. Related Background of the Invention
A multi-core optical fiber with a plurality of cores extending along the fiber axis (center axis) in a common cladding is expected as an optical transmission line that can transmit a large volume of information. For example, J. Lightwave Technol., Vol. 30, No. 4, pp. 583-589, February 2012 (Non Patent Literature 1), ECOC2011, p. Mo. 1. LeCervin. 1 (Non Patent Literature 2), Opt. Express, Vol. 19, No. 26, pp. B543-B550, November 2011 (Non Patent Literature 3), Opt. Lett., Vol. 36, No. 23, pp. 4626-4628, December 2011 (Non Patent Literature 4), OFC2012, p. OM2D.5 (Non Patent Literature 5), Opt. Express, Vol. 20. No. 9, pp. 10100-10105, April 2012 (Non Patent Literature 6), and OFC2011, paper OWA6 (Non Patent Literature 7), a variety of studies have been conducted for the purpose of transmitting a larger volume of information, on the multi-core optical fiber of this kind.
For increasing the transmission capacity of the multi-core optical fiber (MCF), it is necessary to increase the number of cores forming the multi-core optical fiber or to increase the transmission capacity of each of the individual cores forming the multi-core optical fiber. As methods of the latter, Non Patent Literatures 2 to 5 disclose the studies to increase the effective area (Aeff) of the multi-core optical fiber. Non Patent Literature 1 discloses MCFs reducing transmission loss and crosstalk, and Non Patent Literature 6 discloses MFCs reducing crosstalk between cores. It is also necessary to investigate an improvement in optical signal-to-noise ratio (OSNR) of signal light after propagation through the cores, for increase in the transmission capacity of each of the individual cores embedded in the MCF. Non Patent Literature 7 describes the study on an improvement in OSNR in a single-core optical fiber.